Due to the extremely high population of the main world, Azun makes extensive use of arcologies, completely self-contained cities built onto tiny tracts of land. On Azun, these are soaring towers three kilometers high, springing from square bases two kilometers on a side. Such "cities" can comfortably house populations in excess of 1.5 million persons, including not only living space but also nearly every other facet essential for life to flourish. Each such city thus covers only 4 square kilometers of land surface, concentrating the population in a very small area. Therefore, the majority of the land area of Azun can be used for other purposes, including areas for resource exploitation, agriculture, and wilderness reserve.